Synergistic Strengthening and Toughening the Interphase of Composites by Constructing Alternating “Rigid‐and‐Soft” Structure on Carbon Fiber Surface

Abstract

strength, [7] while weakening the interphase can produce additional toughness via fiber debonding and plastic deformation of the interfacial layer. [8] Therefore, engineering the interphase so as to solve the conflict between strength and toughness affords a good opportunity.Nacre, a unique microscale architecture of "brick-and -mortar" that can reform after breaking, endows it with pre-eminent mechanical strength and toughness. [9] Thus, considerable attentions have been contributed to mimic this delicate structure, aiming at gaining exceptional mechanical properties. Different inorganic materials, including graphene, [10] layered double hydroxide (LDH), [11] nanoclay, [12] man-made CaCO 3 , [13] Al 2 O 3 , [14] carbon nanotube (CNT), [15] and TiO 2 , [16] have been employed as "bricks" in fabrication of analogous nacre film materials. Observation of these nacre-like films indicates that the introduction of adequate reinforcing components and appropriate interfacial interactions over several distinct scales are keys affecting the mechanical properties. Inspired by these, whether construction of an composite interphase with nacre-like layered structure can simultaneously enhance the composites' interfacial strength and toughness?Layer-by-layer (LbL) assembly provides a good approach to fabricate such nacre-like layered structure at interphase region, since it has been proved to be a facile way for the fabrication of hierarchical nanostructured layers on various substrates via electrostatic interaction between differently charged materials. [1,6,17] To manifest the critical characteristics of natural nacre, a LDH/poly(sodium-4-styrenesulfonate) nanostructured coating over the surface of glass fiber by LbL was reported by Luca et al., [8] which increased the interfacial shear strength (IFSS) and debonding toughness by 30% and 162%. In addition, the LbL method has been employed to deposit graphene oxide (GO)/aramid nanofiber multilayers, [18] GO/SiO 2 multilayers, [19] and CNT coatings [20] on glass fiber or carbon fiber surface to improve interfacial adhesion of composites.Polydopamine (PDA) and other catechol compounds, due to their outstanding adhesive property and the role of providing platform for secondary reactions, are highly sought after being used to modify the inert surface of carbon fibers. [21][22][23][24][25] Moreover, PDA has dense aromatic structures in its molecular Interphase with nacre-like structured multilayer is constructed by alternatively depositing two polymers, respectively "rigid" polydopamine (PDA) and "flexible" polyether amine, on carbon fiber surface via the layer-by-layer (LbL) approach. The optimal interfacial strength and toughness are achieved for composites with three layers of PDA/polyether amine, respectively, 39.2% and 99.8% superior to the untreated fiber composites. The outstanding mechanical properties are mainly ascribed to the synergistic interactions of covalent bond, hydrogen bonding, and π-π stacking among fiber, multilayer, and matrix by transferring stress and bridgin...

Constructing a Double Alternant “Rigid-Flexible” Structure for Simultaneously Strengthening and Toughening the Interface of Carbon Fiber/Epoxy Composites

“…After PDA modification, more characteristic function groups of PDA emerged, including the stretching of C-H in the benzene ring at 3018 cm −1 , the stretching vibration of indole ring at 1560 cm −1 and shearing vibration of aromatic C=N at 1390 cm −1 [ 25 , 26 ], suggesting the presence of PDA and a Schiff base reaction occurring on the fiber surface. The intensity of the peak at 2800–2980 cm −1 became higher, indicating the presence of a Michael reaction [ 15 ].…”

“…The “rigid-flexible” architectures inspired by the nacre have drawn a lot of attentions because it can endow composites with prominent mechanical strength and toughness [ 13 ]. Inorganic nanoparticles are usually selected as “rigid” components to incorporate in the interface for improving mechanical strength, such as graphene, nanoclay, carbon nanotube (CNT) and TiO 2 [ 14 , 15 , 16 , 17 ]. Nevertheless, in most cases, nanoparticles need to be pretreated in order to introduce active sites to increase the interaction with carbon fiber and matrix resin.…”

Constructing a Rigid-and-Flexible Twin-Stage Gradient Interphase through Starlike Copolymer Coating on Carbon Fibers: A Route for Enhancing Interfacial Properties of Composites

“…The stiffened modulus intermediate layer formed by TAPc would increase the cross-linking density of the interphase and shield crack propagation from touching the fiber surface, whereas the constrained plastic deformation of the interphase limited the release of thermal residual stresses during curing and the efficiency of crack blunting. − On the other hand, the flexible interphase formed using a ductile polymeric material would act as macromolecular coupling agents between the fiber and matrix, − which improves the potential energy-absorbing capacity but reduces the adhesion force between the CF and resin matrix . In view of the design of the interfacial structure with both high stiffness and suitable toughness, − the rigid-and-flexible interphase with rigid/soft structures was proposed as a prospective strategy, among which the rigid component served as the robust shielding layer to deflect the crack path and the soft component acted as a stress-relief medium by inducing viscoplastic energy dissipation. − …”

“…Generally, the rigid-and-flexible interphase was constructed by block or branched copolymers consisting of π-conjugate organic molecules (rigid component) bonded covalently by polymer chains (soft component). ,, According to the work of Deng et al, a diblock copolymer hydroxyl-terminated poly­( n -butylacrylate)- b -poly­(glycidyl methacrylate) (HO-PnBA- b -PGMA) was synthesized by atom-transfer radical polymerization (ATRP) and introduced into the interphase between the CF and epoxy resin, proving that the length of the PGMA block had a great influence on the interfacial properties of the CF composite . PGMA and poly (styrene- co -maleic anhydride)-grafted multiwalled carbon nanotubes were spray-coated onto the surface of CF fabrics by Yao et al, which established the interphase consisting of the PGMA soft component to provide stress dissipation accompanied by stable fiber slippage .…”

From brittle‐to‐ductile fracture of polymer composites: The incorporation of energy dissipation mechanisms by carbon nanotubes‐based multilayered interface

“…[10,12] Recent studies have shown the capability of developing functional materials through the incorporation of thin films on reinforcing agents' surface by using the layer-by-layer (LBL) deposition method. [13][14][15][16] In this work, polypropylene composites with hybrid interface were produced by alternatively depositing two polymers on the glass fiber (GF) surface, poly(diallyldimethylammonium chloride) (PDDA) and poly (sodium 4-styrenesulfonate) (PSS) containing oxidized multiwalled carbon nanotubes (MWCNT-COOH), via the LBL method. [16,17] For obtaining a clear description of the influence of the designed interface on the mechanisms of energy relief during crack propagation, in situ tensile tests were monitored by phase-contrast tomography (PCT) using synchrotron radiation.…”